Magnetic centering device for butt sealing machines



June 1, 1954 w J. LYTLE 2,679,713

. MAGNETIC CENTERING DEVICE FOR BUTT SEALING MACHINES Filed Sept. 22, 1951 A yeg9 1 Mowvr' M (lumen/Iva INVENTOR W I LYTZE.

g gg glz Patented June 1, 1 954 MAGNETIC CENTERING DEVICE FOR BUTT SEALING MACHINES Walter James Lytle, Madison County, Ky., as-

signor to Westinghouse Electric Corporation, East Pittsburgh, Pa., a corporation of Pennsylvania Application September 22, 1951, Serial No. 247,863

3 Claims.

' This invention relates to sealing machines and, more particularly, to a magnetic centering device for a sealing machine spindle or head.

In the manufacture of incandescent lamps, particularly the miniature type, one of the major items of production shrinkage is improper or offcenter sealing of the mount with respect to the bulb or envelope. Under the present method of sealing, the bulb is secured in an inverted vertical position in the bulb adapter or cup by vacuum. The mount is loaded into the bulb and positioned thereon by the force of gravity and the engagement of the pre-formed external portions of the Dumet leading-in conductor in centering slots provided in the bulb adapter. Dumet is the trade name for wire having a nickel-iron core enclosed in a copper sheath which has a total thickness approximately 25% of the finished wire diameter.

A defect in the present method is the lateral movement, during sealing of the external portions of the leads, in centering slots wherein sufficient clearance is required. Further, due to the flexible nature of the leading-in conductors the external portions thereof do not fall into the'centering slots properly during insertion of the mounts into the bulbs. Again-since the mount is light, the force of gravity is not sufiicient to maintain the mounts position in the bulb on the sealing head, which may vibrate as it rotates. Also, at thev butt sealing position of the sealing machine where the exhaust tubulation, bulb, and the. leading-in conductors of the mount are pressed together, gravitational force is not enough to prevent lateral displacement of the mount.

Hence it has been found advantageous, according to my invention, to employ the force of magnetism in addition to the force of gravity to position the mount centrally with respect to the bulb during sealing. Permanent magnets located symmetrically at the sides of the bulb adapter or holder, attract the nickel-iron core of the Dumet leading-in conductors of the mount, thus positioning the mount, as desired, in relation to the bulb.

In its general aspect, the present invention has the object of overcoming the aforementioneddisadvantages of the prior art gravitational centering devices for butt sealing incandescent lamps and the like.

A specific object of the present invention is the elimination of the centering slots in the bulb adapter.

Another object is the elimination of the sealing of improperly centered amounts in the bulbs A further object is a mount centering device employing the force. of magnetism in addition to the force of gravity to center the mount relative to the bulb during the butt sealing operation.

A still further object is a mount centering device having permanent magnets symmetrically at the sides of the bulb adapter.

Other objects and advantages of the invention will appear to those skilled in the art to which it appertains as the description proceeds, both by direct recitation thereof and by implication from the context.

Referring to the accompanying drawing, in which like numerals of reference indicate similar arts throughout the several views:

Fig. 1 is a side view of the centering device of my invention symmetrically amxed about a bulbadapter of a conventional miniature lamp sealing head assembly and showing the miniature lamp bulb and mount being loaded into the bulb adapter;

Fig. 2 is a side view, partially in section, of the sealing head assembly of Fig. l and showing the mount and bulb of Fig. 1 loadedin the bulb adapter and an exhaust tube in a holder mechanism ready for sealing;

Fig. 3 is a view of the sealing head, of Fig. 1, along line III-+111, in the direction of the arrows;

Fig. 4 is a perspective View of the bulb adapter and, the centering device of my invention;

Fig. 5 is a side view of the sealed lamp and Fig. 6 is a schematic diagram of a 16 head butt sealing machine.

Referring to the drawing and, more particularly, to Figs. 1 and 2, a-rotatable sealing head assembly is designated, by the reference numeral 10. This sealing head assembly 10 comprises a sealing head shaft assembly I2, a sealing head I4 located on said shaft assembly, a magnetic centering device [6 of my invention about said head [4 and an exhaust tube holder mechanism I8 on said head assembly Ill.

Sealing head shajt assembly This sealing head shaft assembly 12 may consist, as shown in the present embodiment, of a partially hollow shaft 20 slidable-in a sleeve 22, and about said sleeve a platform 24-and a driven gear 26 for rotating the head assembly 10. Between platform 24 and gear 260m shaft 20 is the indexing table 28 of abutttsealing machine (not shown) for supporting the sealing head assembly l0. and having a bushing 30 about sleeve 22 of shaft 20.

Th s. shaft 20 .(Fig.,2);has. a reducedportion 3| at its upper end on which is fitted the sealing head i 4, and an axial pocket 32 opening upwardly and extending substantially of its length to close proximity with the lower surface of table 28. The bottom of shaft 28 rests on a cam track 34 which controls the vertical travel of head assembly ID with respect to gear 26 and table 28. Near the lower portion of pocket 32, an annular groove 36 having a length slightly greater than the vertical travel of the sealing head assembly in, is connected to pocket 32 by radial holes 38 cut through the wall of shaft 26 between groove 36 and pocket 32. Below the bottom of pocket 62, and adjacent driven gear 26, a vertical keyway 36 having a length similar to that of groove 36 is provided in the outer surface of shaft 28, for receiving the inner end of a set screw of driven gear 26, as hereinafter explained.

The sleeve 22 extends about shaft substantially the combined depths of platform 24, gear 26 and table 28. It provides bearing surface for the head assembly I 8 which is vertically slidable therein by means of cam track 34. When the sealing head assembly I8 is in the loading position of Fig. 2, and at the lowest point of its vertical travel, a groove 40 provided in the outer surface of sleeve 22 is juxtaposed near the bottom of groove 36 in shaft 28. Radial holes 42 cut through the wall of sleeve 22 from groove 46 connect said groove 48 to the groove 36 in shaft 28.

The platform 24, as shown in Fig. 2, suitably circular in plan and T-shaped in vertical section, has a hole near its periphery for mounting exhaust tube holder mechanism [3, as hereinafter explained. It is secured to sleeve 22 by means of a screw 44. The platform rotates on the upper surface of the abutting indexing table 28.

The driven gear 26 for rotating sealing head assembly I0, as shown in Fig. 2, abuts the lower surface of table 28 on shaft 28 and has an appropriate inverted T-shaped vertical cross section. A screw 48 extending through the vertical or shank portion of gear 26 is keyed into keyway 39 in shaft 28, thereby locking gear 26 to shaft 2c and permitting vertical travel of head assembly 18 with respect to gear 26 and table 28. Table 28 contains a vacuum line 46 which registers with groove in sleeve 22 for evacuating the pocket 62 of the shaft 28 as hereinafter described.

Sealing head The sealing head [4 comprises a cylindrical lower portion or hollow supporting member 50 which is supported on the reduced upper end portion 3| of shaft 20, and a bulb adapter or holder 52 of suitable non-magnetic material, such as brass. This holder 52 has a straight-sidedupper portion 53 and. a flanged bottom portion 54 which is press-fitted into an axial cavity 56 in the lower portion 58 of the head M.

The upper end of section 53 has a bulb cavity 58 with an axially conical upwardly opening pocket 56 for centering a bulb 60 loaded with a mount 62. External portions 64 of leading-in conductors 66 of the mount 62 are pre-formed before loading. The top edge of upper portion 53 of the holder 52, is suitably beveled downwardly at approximately to conform to the pre-formed external portions 64 of conductors 66. An axial hole 68 in the flnage-like bottom portion 54 of holder 52 extending into upper portion 53 acts as a continuation of pocket 32 in shaft 26. Four vertical holes-l0, one-arranged 4 axially and three arranged in spaced circular sequence in the present showing of Fig. 3, connect the pocket 59 of bulb cavity 58 with hole 68.

Magnetic centering device As shown in Figs. 2, 3 and 4, and more particularly in Fig. 3, the magnetic centering device [6 of my invention consists of a permanent magnet member 12 and a balancing member 14. This member 12, as shown in Fig. 4, has a body 16 of general semi-cylindrical configuration, cast with two diametrically opposed permanent magnet centering tips 18 which project above its upper surface near the open end of the body. Both the body 16 and the tips 18 are suitably Alnico, the trade name for a permanent magnet alloy material having the following approximate composition:

The outside diameter of body 16 and tips 18 conforms to the outside diameter of the lower portion 58 of head M. The vertical inside surfaces of tips 18 are straight and parallel to the adjacent sides of upper portion 53 of head l4 with an air space therebetween for preventing conduction of heat from adapter 52 to tips 18. The top of tip 18 is tapered downwardly at the same angle as the upper edge of adapter 52, but it projects above said edge of adapter 52 to prevent contact between the external portions 64 of conductors 66 and said adapter edge. As shown in Fig. 3, these tips 18 have a frusto-sector shaped horizontal cross section tapering inwardly toward the center of the axis of the magnetic centering device l6. Both tips 18 are supported on each vertical side by a non-magnetic support 80, suitably of brass. These supports which are cast to the body 16 and the tips 18 conform in configuration to the tips 18 and facilitate centering of the lead-in conductor 66 on tips 18, as hereinafter explained.

The magnetic member 12 is secured to the flange of the bottom portion 54 of holder 52 by means of screws 82 (Fig. 4). Washers 84 (Fig. 1) on screws 82 between body 16 and member 12 and said flange provide an air space therebetween to impede heat conduction to magnetic member 12.

The balancing member 14 (Figs. 3 and 4) suitably a non-magnetic material such as brass is similar in shape to body 16 of magnetic member 12 and. is weighted to balance the magnetic centering device I6 about the axis of sealing head assembly ID as said assembly rotates on the sealing machine. It is secured to the flange of lower portion 54 of holder 52 by a screw 82 (Fig. 3). A suitable air space between adjacent surfaces of body 16 and member 14 is provided to eliminate heat conduction. Flat baffles 85 (Fig. 2), of suitable non-magnetic material, such as brass, may be mounted above the centering tips 18 and below the plane of the sealing fires (not shown) to protect the tips from the fires.

Exhaust tube holder mechanism On the gamers upperendof shaft 85 are a pair of'rotatable Butt sealing machine It will be understood that a conventional butt sealing machine, for example, a 16 head machine, as shown schematically in Fig. 6, has 16 heads similar to sealing head assembly It). At the front of the machine, the bulb 6i] and mount 62 are loaded as hereinafter explained. At station number i or 2 a positioning finger (not shown) pushes bulb 60 into bottom pocket 59 of bulb cavity 58, and the vacuum line is opened. Tubulation 93 is loaded into holder mechanism 18, in station 3. At the fourth station or port, the neck of bulb 60 is straightened and tubulation 94 is pushed down to a predetermined position above the neck of bulb 68. In station 5 the cam track 34 raises the bulb GI] and the mount 62 into contact with the bottom portion of tubulation 94. In stations 6 through it the seaiing head assembly is rotated by means of. driven gear 3 26' and stationary. sealing fires are applied to the parts in gradually increasing temperature steps for sealing the tubulation, mount, and bulb together. In station it the sealing head assembly i0 ceases to rotate and head it is lowered by cam track 35, thereby pulling down the mount and bulb and forming a constriction in the tubulation above the seal as shown in Fig. 5. The sealed lamp is automatically unloaded in station i5 and the bottom portion 59 of cavity 58 in bulb adapter 52 is flushed in station !6 to remove broken particles of glass and dirt therefrom.

Operation According to my invention, the butt sealing machine is loaded in the No. I and No. 2 stations by inserting an inverted bulb 60 into bulb cavity 58 of the head 14 with the bulb dome resting in the bottom pocket 59 of said cavity. The mount 62 having external portions 64 of leading-in conductors 86 pre-forrned at the desired 45 angle from the mount axis is inserted into bulb 60 with the bends in the conductors 66 resting on the bulb neck. The additional surface provided on each side of tips "(8 by supports 80 keep the external portions 6d of conductors 66 in the plane of tips '58 and said portions 64 are positioned automatically by the magnetic tips 78 without undue operator manipulation. The external portions 64 are positioned and securely held on centering tips 56 by the magnetic force, the permanent magnet tips 18 exert on the conductors 66 as well as the gravitational force exerted by the mount 62 on the bulb neck.

The bulb is securely aligned and held by a vacuum created by the vacuum line pumping through holes HI and 68 in bulb adapter 52; pocket 32, holes 38 and groove 36 in shaft 20; holes 42 and groove 46 in bushing 22; and vacuum line 46. As the external portions 64 are unsupported between tips 18 and the bulb neck, the action of the positioning finger in station 3 combined with the magnetic force causes a sag and a resultant spring action in the unsupported length, thereby firmly pressing the bulb 60"- against the bottom pocket 59 of bulb cavity'58 and maintaining the bulb 60 and mount 62 in" this position during the remainder of the'sealing operation, despite the vibrationof head'assembly' I0 due to rotation or other causes.

Thus it will be seen from the foregoing descrip tion that I have achieved a magnetic centering device -I 6' for a sealing head assembly lc employing the force of. magnetism in additionto the force of 'gravity to center the mount relative to the bulb during the sealingoperation, This mag netic centering devicehas apermanent magnetcentering tip 78 located symmetrically at thesides of the bulb adapter 52 of the sealing head! 4.

Although a preferred embodiment of my invention has been disclosed, it will .beunderstood that modifications may be made within the spirit and scope of the appended claims.

I claim:

1. A sealing head assembly for a butt sealingsleeve above said table, and a driven-gear on said sleeve and keyed to said shaft below said table;

a sealing head on said shaft, said sealing headcomprising a lower hollow supporting member on the upper end of said shaft, a non-magnetic bulb holder having a flanged bottom portion provided with a hole therethru and fitted into the hollow portion of said supporting member and an upper portion provided with a bulb cavity, a conical upwardly opening pocket for centering a bulb therein and a plurality of holes connecting said pocket with the hole of said flanged bottom portion; an exhaust tube holder mechanism on said platform, a magnetic centering device on and about said head, means for rotating and vertically reciprocating said sealing head with respect to said table, and means for evacuating said hollow shaft and to apply vacuum to said bulb holder.

2. A sealing head assembly for a butt sealing machine having a rotatable indexing table, and comprising: a sealing head shaft assembly supported on said table, said sealing head shaft assembly consisting of a sleeve fixed to said table, a partially hollow shaft rotatable and vertically reciprocable in said sleeve, a platform on said sleeve above said table, and a driven gear on said sleeve and keyed to said shaft below said table; a sealing head on said shaft, said sealing head comprising a lower hollow supporting member on the upper end of said shaft, a non-magnetic bulb holder having a flanged bottom portion provided with a hole therethru and fitted into the hollow portion of said supporting member and an upper portion provided with a bulb cavity, a conical upwardly opening pocket for centering a bulb therein and a plurality of holes connecting said pocket with the hole of said flanged bottom portion; an exhaust tube holder mechanism on said platform, said exhaust tube holder mechanism comprising a vertical tube holder shaft secured at one end to said platform, a pair of rotatable gears on the upper end of said tube holder shaft, and a spring-biased tubulation holder arm extending from each of said gears provided with recesses in their outer ends for securing a tubulation therein; a magnetic centering device on and about said head, means for rotating and vertically reciprocating said sealing head with respect to said table, and means for evacuating said hollow shaft and to apply vacuum to said bulb holder.

3. A sealing head assembly for a butt sealing machine having a rotatable indexing table, and comprising; a sealing head shaft assembly supported on said table, said sealing head shaft assembly consisting of a sleeve fixed to said table, a partially hollow shaft rotatable and vertically reciprocable in said sleeve, a platform on said sleeve above said table, and a driven gear on said sleeve and keyed to said shaft below said table; a sealing head on said shaft, said sealing head comprising a lower hollow supportin member on the upper end of said shaft, a non-magnetic bulb holder having a flanged bottom portion provided with a hole therethru and fitted into the hollow portion of said supporting member and an upper portion provided with a bulb cavity, a conical upwardly opening pocket for centering a bulb therein and a plurality of holes connecting said pocket with the hole of said flanged bottom portion; an exhaust tube holder mechanism on said platform, said exhaust tube holder mechanism comprising a vertical tube holder shaft secured at one end to said platform, a pair of rotatable gears on the upper end of said tube holder shaft and a spring-biased tubulation holder arm extending from each of said gears provided with recesses in their outer ends for securing a tubulation therein, a magnetic centering device on and about said head, said magnetic centering device comprising a permanent magnet member about said bulb holder, secured to said flanged bottom portion of said sealing head, said permanent magnet member having a body provided with an open end and two diametrically opposed permanent magnet centering tips projecting above the upper surface of said permanent magnet member and said bulb holder at the open end of said body and a non-magnetic support on either side of each of said tips, said tips and said supports tapering downwardly from the center of the axis of said device for support and engagement thereon of the outer portions of lead-in conductors, and a non-magnetic balancing member secured to said flanged bottom portion of said sealing head and weighted to balance the magnetic centering device about the axis of said sealin head assembly as said assembly rotates on the sealin machine, means for rotating and vertically reciprocating said sealing head with respect to said table, and means for evacuatin said hollow shaft and to apply vacuum to said bulb holder.

References Cited in the file of this patent UNITED STATES PATENTS Number 

